Dust collector including filter cleaning mechanism

ABSTRACT

A dust collector for use with a hand-held power tool. The dust collector includes a housing, a motor positioned in the housing, and a telescoping suction pipe coupled to the housing. The dust collector also includes a suction fan coupled to the motor and operable to generate a vacuum in the suction pipe. The dust collector further includes a dust container coupled to the housing and positioned upstream of the suction fan, and a filter at least partially arranged in the dust container. The dust collector also includes a filter cleaning mechanism including a solenoid configured to be actuated by a controller to dislodge dust from the filter when either the motor or the suction fan transitions from an active state to an inactive state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/688,227, filed on Nov. 19, 2019, which claims priority toU.S. Provisional Patent Application No. 62/879,695, filed Jul. 29, 2019,and to U.S. Provisional Patent Application No. 62/814,934, filed Mar. 7,2019, and to U.S. Provisional Patent Application No. 62/801,497, filedFeb. 5, 2019, and to U.S. Provisional Patent Application No. 62/769,396,filed Nov. 19, 2018, the entire contents of all of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly todust collectors for use with power tools.

BACKGROUND OF THE INVENTION

Dust collectors are typically used in tandem with hand-held drillingtools such as rotary hammers to collect dust and other debris during adrilling operation to prevent dust and other debris from accumulating ata worksite. Such dust collectors may be attached to a rotary hammer toposition a suction inlet of the collector proximate a drill bit attachedto the rotary hammer. Such dust collectors may also include an on-boarddust container in which dust and other debris is accumulated. Such dustcontainers are often removable from the dust collector to facilitatedisposal of the accumulated dust and debris.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a dust collector for use with ahand-held power tool. The dust collector includes a housing, atelescoping suction pipe coupled to the housing, and a suction fanpositioned within the housing and operable to generate a vacuum in thesuction pipe. The suction pipe is configured to telescope toward andaway from the housing. The suction pipe includes an outer pipe supportedby the housing, and an inner pipe slidably received into the outer pipe.

The invention provides, in another aspect, a dust collector for use witha hand-held power tool. The dust collector includes a housing, a motorpositioned in the housing, and a telescoping suction pipe coupled to thehousing. The dust collector also includes a suction fan coupled to themotor and operable to generate a vacuum in the suction pipe. The dustcollector further includes a dust container coupled to the housing andpositioned upstream of the suction fan, and a filter at least partiallyarranged in the dust container. The dust collector also includes afilter cleaning mechanism including a solenoid configured to be actuatedby a controller to dislodge dust from the filter when either the motoror the suction fan transitions from an active state to an inactivestate.

The invention provides, in another aspect, a dust collector for use witha hand-held power tool. The dust collector includes a housing, and amotor having a motor shaft rotatable in a first rotational direction andin a second rotational direction opposite the first rotationaldirection. The dust collector also includes a telescoping suction pipecoupled to the housing, and a suction fan coupled to the motor andoperable to generate a vacuum in the suction pipe when the motor shaftrotates in the first rotational direction. The dust collector furtherincludes a dust container coupled to the housing and positioned upstreamof the suction fan, and a filter at least partially arranged in the dustcontainer. The dust collector also includes a filter cleaning mechanismconfigured to dislodge dust from the filter when the motor shaft rotatesin the second rotational direction.

The invention provides, in another aspect, a dust collector for use witha hand-held power tool. The dust collector includes a housing, a motorpositioned in the housing, and a telescoping suction pipe coupled to thehousing and configured to telescope toward and away from the housing.The dust collector also includes a suction fan coupled to the motor andoperable to generate a vacuum in the suction pipe. The dust collectorfurther includes a dust container coupled to the housing and positionedupstream of the suction fan, and a filter at least partially arranged inthe dust container. The dust collector further includes a filtercleaning mechanism including a hammer movable between a loaded position,in which the hammer is biased toward engagement with the filter, and areleased position, in which the hammer impacts the filter to dislodgedust therefrom. As the suction pipe telescopes toward and away from thehousing, the suction pipe engages the filter cleaning mechanism to causethe hammer to move between the loaded and released positions.

The invention provides, in another aspect, a dust collector for use witha hand-held power tool. The dust collector includes a housing, a motorpositioned in the housing, a suction pipe coupled to the housing, and asuction fan coupled to the motor and operable to generate a vacuum inthe suction pipe. The dust collector also includes a dust containercoupled to the housing and positioned upstream of the suction fan, and afilter at least partially arranged in the dust container. The dustcollector further includes a monitoring system configured to detectclogs in the filter by detecting a characteristic value of the dustcollector and determining whether the characteristic value exceeds apredetermined threshold.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a power tool assembly including adust collector mounted to a rotary power tool.

FIG. 2 is a rear perspective view of the dust collector and rotary powertool of FIG. 5 .

FIG. 3 is a rear perspective view of a dust collector in accordance withan embodiment of the invention.

FIG. 4 is a front perspective view of the dust collector of FIG. 3

FIG. 5 is a front perspective view of another embodiment of a dustcollector including a telescoping suction pipe.

FIG. 6 is an extension nozzle for use with any of the dust collectors ofFIGS. 1-5 .

FIG. 7 is a handle assembly for use with any of the dust collectors ofFIGS. 1-5 .

FIG. 8 is a partial cross-sectional view of the dust collector of FIG. 3.

FIG. 9 is an enlarged, exploded perspective view of the dust collectorof FIG. 3 , illustrating a dust container and a filter.

FIG. 10 is a cross-sectional view of a vacuum hose adapter for use withany of the dust collectors of FIGS. 1-5 .

FIG. 11 is an enlarged view of a first embodiment of a filter cleaningmechanism for use with any of the dust collectors of FIGS. 1-5 .

FIGS. 12A and 12B are plan views of a solenoid of the filter cleaningmechanism of FIG. 11 .

FIG. 13 is a partial cross-sectional view of a second embodiment of afilter cleaning mechanism for use with any of the dust collectors ofFIGS. 1-5 .

FIG. 14 is a perspective view of a third embodiment of a filter cleaningmechanism for use with any of the dust collectors of FIGS. 1-5 .

FIGS. 15A-15C are plan views of a fourth embodiment of a filter cleaningmechanism for use with any of the dust collectors of FIGS. 1-5 .

FIG. 16 is a perspective view of a dust collector according to anotherembodiment, including another embodiment of a stop assembly in a firstarrangement.

FIG. 17 is a perspective view of the stop assembly of FIG. 16 in asecond arrangement.

FIG. 18A is a perspective view of a stop mechanism according to oneembodiment.

FIG. 18B is a cross-sectional view of the stop mechanism of FIG. 18Ataken along line 18-18.

FIG. 19 is a perspective view of a telescoping suction pipe according toanother embodiment.

FIG. 20 is an exploded view of the suction pipe of FIG. 19 .

FIG. 21 is a perspective view of another embodiment of a telescopingsuction pipe.

FIG. 22 is an exploded view of the suction pipe of FIG. 20 .

FIG. 23 is a partial cross sectional view of an adapter for attaching anauxiliary handle to the housing of any of the dust collectors of FIGS.1-5 and 16 .

FIG. 24 is a perspective view of an adapter according to anotherembodiment.

FIGS. 25A-25B are cross-sectional views of the adapter of FIG. 24 in aclosed and an open position, respectively.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a power tool assembly 100 including a powertool 1 and a dust collector 50. As will be described in more detailbelow, the dust collector 50 is operable to collect dust and otherdebris from a workpiece during a drilling and/or hammering operationperformed by the power tool 1 to maintain the user's work areasubstantially clear of dust. In the illustrated embodiment, the powertool 1 is a drilling machine or rotary power tool, which may beconfigured as a percussion rotary power tool, a rotary hammer, or ahammer drill. The power tool 1 includes a housing 2 in which a spindle(not shown) is drivable in a rotary manner about an axis of rotation 3.For this purpose, the rotary power tool 1 includes an electric motor(not shown) for driving rotation of the spindle. The illustrated powertool 1 is powered by a battery 4, such as a rechargeable battery pack.In other embodiments, the power tool 1 may include a cord to enable thepower tool 1 to be powered by AC power. The rotary power tool 1 is alsoequipped with a handle 5. It may thus be operated by hand andaccordingly be designated a hand-held rotary power tool 1.

The rotary power tool 1 is also equipped with a chuck 6 that is drivablein a rotary manner about axis of rotation 3 via the spindle. The chuck 6serves to hold a working tool 12, particularly a drilling tool, whichmay be a drill bit, a hammer drill bit, or a masonry drill bit. When thedrill bit 12 is in place, it rotates about the axis of rotation 3, whichwill also be referred to in the following as the axis of rotation 3 ofthe power tool 1. Adjacent to the chuck 6, the housing 2 of rotary powertool 1 is furnished with a clamping neck 7, which has a cylindricalshape in the illustrated embodiment. The clamping neck 7 is normallyused for mounting an additional handle.

The rotary power tool 1 shown in FIGS. 1 and 2 is equipped with a dustsuction device or dust collector 50 in accordance with an embodiment ofthe invention. The dust collector 50 constitutes a separate device fromthe rotary power tool 1, and may be attached and detached to the rotarypower tool 1 without using tools. The dust collector 50 may be poweredindependently of the power tool 1, for example, by a rechargeablebattery 54. In the illustrated embodiment, the dust collector 50 and thepower tool 1 include separate batteries 54, 4, respectively, each ofwhich may be interchangeably coupled with the power tool 1 and the dustcollector 50. In other words, the dust collector 50 and the power tool 1may be independently powered using identical batteries 54, 4. However,in other embodiments, the dust collector 50 and the power tool 1 mayshare a power source. For example, the dust collector 50 may be poweredby the battery 4 of the power tool 1. In addition, in some embodiments,one or both of the power tool 1 and the dust collector 50 may include acord that provides AC power.

FIGS. 3 and 4 illustrate another embodiment of a dust collector 110detached from the power tool 1. The dust collector 110 includes ahousing 118, a suction pipe 122 coupled to the housing 118, an electricmotor 126 (FIG. 8 ) positioned in the housing 118 and powered by abattery 154, a suction fan 130 (FIG. 8 ) driven by the electric motor126 and operable to generate a vacuum in the suction pipe 122, and adust container 134 (FIG. 8 ) coupled to the housing 118 and positionedupstream of the suction fan 130. In addition, the dust collector 110includes a handle assembly 138 that supports the power tool 1 in aside-by-side relationship with the dust collector 110.

The suction pipe 122 of the dust collector 110 telescopes relative tothe housing 118. As the drill bit 12 plunges into the workpiece, thesuction pipe 122 retracts into the housing 118 of the dust collector 110in a telescoping manner. Therefore, the drill bit 12 can only extendinto the workpiece an equal depth as the suction pipe 122 retracts. Thefarther the suction pipe 122 can retract, the greater drilling depth isavailable for the drill bit 12. Accordingly, making the suction pipe 122a telescoping tube increases the drilling depth of the drill bit 12.

For this purpose, the suction pipe 122 includes an outer pipe 140arranged on the housing 118 and an inner pipe 142 arranged coaxiallytherewith and positioned inside the outer pipe 140 so as to be slidablein a telescoping manner (FIG. 3 ). The inner pipe 142 carries a suctionhead 230. The outer pipe 140 is attached to the housing 118 so as to beaxially adjustable. The outer pipe 140 thus enables the suction pipe 122to be adjusted axially so that the dust collector 110 may be adapted tothe differing lengths of the drilling tool with which it is used, forexample a drill bit, a masonry drill bit, or a hammer drill bit. Thetelescoping capability of the suction pipe 122 enables the dustcollector 110 to be adjusted automatically and steplessly to thedrilling depth while the rotary power tool 1 is being operated. As thedepth of the hole created with the drilling tool increases, so the innerpipe 142 extends deeper into the outer pipe 140. The inner pipe 142 maybe braced axially against the outer pipe 140 via a compression spring(not shown). In this way, the inner pipe 142 is pre-tensioned outwardlyto maintain the suction head 230 against the object being drilled.

FIG. 5 illustrates another embodiment of a suction pipe 122 a, whichincludes additional telescoping members. Specifically, in thisembodiment, the suction pipe 122 a includes an outer pipe 140 a coupledto a housing 118 a of the dust collector 110 a, an inner pipe 142 asupporting a suction head 230 a, and an extension pipe 146 a couplingthe outer pipe 140 a to the inner pipe 142 a. The extension pipe 146 aenables the suction pipe 122 a to have a relatively long extended lengthwhile still being able to retract into a compact housing 118 a. Thesuction pipe 122 a may include additional extension pipes 146 a betweenthe outer pipe 140 a and the inner pipe 142 a for additional telescopingcapabilities.

FIGS. 19 and 20 illustrate another embodiment of a suction pipe 550. Thesuction pipe 550 includes an outer pipe 554 and an inner pipe 558. Thesuction pipe 550 is constructed to limit the deflection of the suctionhead 230 (not shown in FIG. 19 ) during use. The inner pipe 558 has aplurality of projections 562 extending radially outward from a maincylindrical body 566 of the inner pipe 558, and along the length of theinner pipe 558. Each of the plurality of projections 562 are configuredto be received within one of a plurality of corresponding recesses 570formed within a main cylindrical body 574 of the outer pipe 554, andextending along the length of the outer pipe 554. Tabs 578 arepositioned between the projections 562 and the recesses 570 to couplethe inner pipe 558 and the outer pipe 554 in a telescoping arrangement.The tabs 578 are positioned at or near the distal end of the outer pipe554.

A plurality of projections 582 are formed along the length of the outerpipe 554 and extend radially outward from the main cylindrical body 574of the outer pipe 554. Each of the projections 582 corresponds to one ofthe recesses 570 and is radially aligned with the underlying recesses570 such that the underlying recess 570 extends into the correspondingprojection 582. Each of the projections 582 includes a lip 586 forreceiving a connector 590 that couples the outer pipe 554 to the housing118 in a telescoping arrangement. In the illustrated embodiment, theprojections 582 include a lip 586 on each side of the projection 582 toengage with a connector 590 on each side of the projection 582.

Accordingly, the suction pipe 550 illustrated in FIGS. 19-20 limitsdeflection of the inner pipe 558 relative to the outer pipe 554. Inparticular, the alignment between the inner pipe 558 and the outer pipe554 is provided by engagement between the projections 562 on the innerpipe 558 and the tabs 578 positioned within the recesses 570 near thedistal end of the outer pipe 554, rather than by the main cylindricalbodies 566, 574 of the inner pipe 558 and the outer pipe 554. Similarly,alignment of the outer pipe 554 with the housing 118 is provided byprojections 582 on the outer pipe 554 with the connectors 590 on thehousing 118. This eases manufacturing tolerances on extruded parts anduses features that are more easily controllable from a manufacturingstandpoint. The illustrated embodiment of the suction pipe 550 includesfour sets of projections 562 and recesses 570. However, in otherembodiments, a greater or fewer number of projections 562 and recesses570 may be utilized.

FIGS. 21 and 22 illustrate another embodiment of a suction pipe 610having an outer pipe 614 and an inner pipe 618 coupled together in atelescoping arrangement. The suction pipe 610 is configured to constrainthe deflection between the outer pipe 614 and the inner pipe 618. Theinner pipe 618 and the outer pipe 614 have a flattened top surface 622and a rounded bottom surface 626. The inner pipe 618 includes a recess630 extending along the length of the inner pipe 618. In the illustratedembodiment, the inner pipe 618 has two recesses 630 extending along thelength of the inner pipe 618. The recesses 630 are positioned near thetransition between the flattened top surface 622 and the rounded bottomsurface 626. The outer pipe 614 includes two ribs 634 protrudingradially inward and along the length of the outer pipe 614. The ribs 634each correspond to the recesses 630 on the inner pipe 618. The outerpipe 614 and the inner pipe 618 are coupled together in a telescopingarrangement by a first bushing 638 and a second bushing 642. The firstbushing 638 is coupled to the inner pipe 618 and the second bushing 642is coupled to the outer pipe 614. The inner pipe 618 and the outer pipe614 are assembled by pushing the inner pipe 618 through the outer pipe614 from the rear end of the outer pipe 614. The suction pipe 610 iscoupled to the housing 118 by two additional bushings 646. The bushings646 are fixed to the outer pipe 614 and arranged to slide within achannel 650 formed by the housing 118.

Referring back to FIGS. 3 and 4 , the suction head 230 of the dustcollector 110 is coupled to the end of the suction pipe 122. The suctionhead 230 includes a hub 234, a hollow arm 238 extending from a side ofthe hub 234, and a shroud 242 coupled to the end of the arm 238. Theshroud 242 defines a suction inlet 246 through which air is drawn duringoperation of the dust collector 110. In the illustrated embodiment ofthe dust collector 110, the arm 238 includes a first portion 243integrally formed with the hub 234 and a second portion 244 integrallyformed with the shroud 242. The second portion 244 is received in thefirst portion 243 and can be positioned at different depths within thesecond portion 244 in order to adjust the distance between the hub 234and the shroud 242. The first portion 243 and the second portion 244 canbe fixed relative to one another by way of a snap-fit, or an over centercam latch. By allowing the hub 234 and the shroud 242 to be moved towardor away from one another, the dust collector 110 can accommodatedifferent size power tools 1.

When the suction inlet 246 is in contact with a workpiece during adrilling operation, the shroud 242 encloses a portion of the drill bit12 and the surrounding region of the work piece to maintain the regionat a sub-atmospheric pressure. In other words, the vacuum created in thesuction pipe 122 and the suction head 230 draws dust and other debrisgenerated during the drilling and/or hammering operation from the shroud242, through the suction pipe 122, for depositing in the container 134.The suction head 230 may be attached to the suction pipe 122 in twodifferent orientations to accommodate placement of the power tool 1 onboth sides of the dust collector 110. A detent arrangement can beutilized to maintain the suction head 230 in either of the positions.

With reference to FIG. 6 , the dust collector 110 may include anextension nozzle 266 removably coupled to the suction pipe 122 via thesuction head 230. The extension nozzle 266 enables the power tool 1 tobe used in constricted areas. In some embodiments, the nozzle may beformed as a single integral piece, while in other embodiments, thenozzle maybe formed by multiple pieces that are coupled together.

With reference to FIG. 7 , the handle assembly 138 includes a handleportion 148, a head portion 150, and an adapter 152. The head portion150 is configured to wrap around the neck of the power tool 1, and isadjustable to different sizes to accommodate power tools 1 withdifferent sized necks 7. The adapter 152 is configured to clamp onto thehousing 118 of the dust collector 110 to secure the handle assembly 138to the dust collector 110. The handle assembly 138 thereby couples thepower tool 1 to the dust collector 110. In the illustrated embodiment,the handle portion 148 includes a grip 160 and a threaded shaft 162. Thehead portion 150 includes an arcuate band 158 that forms a circularopening 168 for receiving the neck 7 of the power tool 1. The circularopening 168 formed by the arcuate band 158 can be constricted andexpanded by rotating the handle portion 148. In particular, each end 156of the band 158 extends through a slit in an end piece 164 of the handleportion 148. The ends 156 of the band 158 are then coupled to a bolt 166that is axially slidable along the threaded shaft 162. As the handleportion 148 is rotated the bolt 166 is axially displaced along thethreaded shaft 162 to either increase or decrease the size of thecircular opening 168.

With reference to FIG. 23 , the adapter 152 includes a fixed clampmember 170 and an opposed, movable clamp member 174 for clamping theadapter 152 to either side of the housing 118. Particularly, the movableclamp member 174 is received within a first notch 178 in the housing118, and the fixed clamp member 170 is received within a second notch182 in the housing 118. The notches 178, 182 are defined in each side ofthe housing 118 to clamp the adapter 152 to either side of the housing118. In the illustrated embodiment of the dust collector 110, a metalreinforcing plate 183 is insert molded with the housing 118 between thenotches 178, 182 such that the clamp members 174, 170 engage bottom andtop edges 184, 185 of the plate 183, respectively. Alternatively, theplate 183 may be omitted.

The adapter 152 also includes a lever 194 for actuating the movableclamp member 174 between an open position in which the movable clampmember 174 is received within the first notch 178 and engaged with thehousing 118. The adapter 152 further includes a resilient member (e.g.,a compression spring 198) that biases the movable clamp member 174towards the fixed clamp member 170 and toward the clamped position. Thelever 194 can be actuated to move the movable clamp member 174 to theopen position. In the illustrated embodiment, the lever 194 can berotated in a counter clockwise direction (as shown in FIG. 23 ), whichpulls the movable clamp member 174 (via a linkage 202) against the biasof the spring 198. In one embodiment, the spring 198 deforms under lessforce than it takes to damage the material forming the notches 178, 182on the housing 118. This ensures that when the dust collector 110 isdropped or otherwise impacted proximate the handle assembly 138, theadapter 152 disengages the housing 118 rather than breaking the portionof the housing 118 between the notches 178, 182.

FIGS. 24 and 25A-25B illustrate an adapter 152 a according to anotherembodiment. In the illustrated embodiment, the adapter 152 a includes afixed clamp member 170 a and an opposed, movable clamp member 174 a forclamping the adapter 152 a to the housing 118. The movable clamp member174 a is received within the first notch 178 of the housing 118, and thefixed clamp member 170 a is received within the second notch 182 in thehousing 118. The adapter 152 a also includes a lever 194 a for actuatingthe movable clamp member 174 a between an open position in which themovable clamp member 174 a is received within the first notch 178 andengaged with the housing 118. The adapter 152 a further includes abiasing member (e.g., a compression spring 198 a) that biases themovable clamp member 174 a towards the fixed clamp member 170 a andtoward the clamped position. The lever 194 a can be actuated to move themovable clamp member 174 a to the open position.

Specifically, the illustrated adapter 152 a includes a sled body 171, asled plate 173, and a sled clamp 175 that interact with the lever 194 aand the biasing member 198 a to adjust the adapter 152 a between theopen and closed positions. In the illustrated embodiment, the sled body171 is integral with the movable clamp member 174 a. The sled plate 173is fixed to the fixed clamp member 170 a. The sled body 171 and the sledclamp 175 are fixed to one another, and are movable with the movableclamp member 174 a relative to the fixed clamp member 170 a. The biasingmember 198 a is positioned between the sled clamp 175 and the sled plate173 to bias the movable clamp member 174 a towards the fixed clampmember 170 a (e.g., upward in FIG. 24 ). When the lever 194 a is rotated(e.g., counter clockwise in FIG. 24 ), the lever 194 a cams against thesled clamp 175 to move the sled body 171 (e.g., downward in FIG. 24 )and, thus, the movable clamp member 174 a away from the fixed clampmember 170 a. In other words, rotation of the lever 194 a moves the sledclamp 175 towards the sled plate 173 and compresses the biasing member198 a to move the movable clamp member 174 a towards the open position.FIG. 25A illustrates the adapter 152 a in the closed position, and FIG.B illustrates the adapter 152 a in the open position.

Referring back to FIGS. 3 and 4 , the dust collector 110 includes a stopassembly 270 to help limit the axial movement of the suction pipe 122 ineither the extended direction, the retracted direction, or both. Inparticular, the stop assembly 270 includes a plunge depth stop 274,which limits the extent to which the suction pipe 122 may retract intothe housing 118, and in turn, limits the extent to which the drill bit12 can plunge into the workpiece. The plunge depth stop 274 is movablealong the length of a rail 278 and is selectively fixed to the rail 278to limit the extent to which the suction pipe 122 may telescope relativeto the housing 118. The stop assembly 270 also includes an extensionstop 280, which limits the extent to which the suction pipe 122 mayextend out of the housing 118. The extension stop 280 is moveable alongthe length of the rail 278 and can be selectively fixed to the suctionpipe 122. This feature can be used to adjust the extension length of thesuction pipe 122 to correspond to the size of the tool bit 12 beingused. For example, when using a 4 inch tool bit 12, the extension lengthof the suction pipe 122 can be reduced to 4 inches to correspond to thelength of the tool bit 12. If the extension length of the suction pipe122 is not limited, then the end of the suction pipe 122 may extend farbeyond the end of the tool bit 12.

In the illustrated embodiment, the rail 278 extends parallel to thesuction pipe 122, and provides additional strength and rigidity to thesuction pipe 122. In addition, the rail 278 may include a ruler (notshown). The ruler is movable with the depth stop 274. As such, theplunge depth of the suction tube 122 may be set with reference tomarkings on the ruler and a reference datum on the housing 118 (e.g., aline or edge on the front of the housing 118 surrounding the suctionpipe 122). For example, should the user of the dust collector 110 andthe power tool 1 desire to plunge the drill bit 12 only two inches intoa workpiece, the user would slide the depth stop 274 relative to thesuction tube 122 until the “2 inch” marking on the ruler is in alignmentwith the reference datum on the housing 118. Thereafter, the suctionpipe 122 is limited to retracting only two inches into the housing 118before the depth stop 274 contacts the housing 118 at which time furtherretraction of the suction pipe 122 is halted.

FIGS. 16 and 17 illustrate another embodiment of a stop assembly 284.The stop assembly 284 includes a plunge depth stop 304 and an extensionstop 308 having similar functionality as the plunge depth stop 274 andthe extension stop 280 described above. Specifically, the plunge depthstop 304 limits the extent to which the suction pipe 122 may retractinto the housing 118, and in turn, limits the extent to which the drillbit 12 can plunge into the workpiece. The extension stop 280 limits theextent to which the suction pipe 122 may extend from the housing 118,based upon a desired length of the tool bit 12. The illustrated stopassembly 284 further includes a rail 286 formed by a first flat bar 288and a second flat bar 292. The first flat bar 288 and the second flatbar 292 are configured to slide (i.e., translate) relative to oneanother. The first flat bar 288 includes a ruler 296 for setting aplunge depth, and is movable with the plunge depth stop 304. The secondflat bar 292 includes a series of holes 300 that are engagable by theplunge depth stop 304 and the extension stop 308 to set the plunge depthand the extension depth, respectively.

FIGS. 16 and 17 each illustrate examples of how the stop assembly 284can be arranged to various plunge depths and extension depths. FIG. 16illustrates the stop assembly 284 arranged to drill a three inch holewhile using an 8 inch bit 12. The plunge depth stop 304 and the firstflat bar 288 are moved together so that the three inch mark on the ruler296 is aligned just outside the housing 118. In addition, the secondflat bar 292 is extended beyond the plunge depth stop 304 in order toaccommodate the length of an 8 inch bit 12. FIG. 17 illustrates the stopassembly 284 arranged to drill a 4 inch hole while using a 4 inch bit12. The plunge depth stop 304 and the first flat bar 288 are movedtogether so that the four inch mark on the ruler 296 is aligned justoutside the housing 118. The second flat bar 292 is aligned with thefirst flat bar 288 (i.e., it does not need to be extended beyond thefirst flat bar 288) because only a 4 inch bit 12 is intended for use inthis arrangement.

FIGS. 18A and 18B illustrate one embodiment of a stop mechanism 310 thatcan be used as the plunge depth stop 304 or the extension stop 308. Thestop mechanism 310 includes a first portion (e.g., button 314) and asecond portion (e.g., housing 318) having a slot in which the secondflat bar 292 is partly received. The button 314 is partially receivedwithin the housing 318, and moveable relative thereto. In the defaultposition, the button 314 is biased toward the second flat bar 292 by aspring 322 in order to clamp the housing 318 onto the second flat bar292. When in the default position, a projection 326 extending from thebutton 314 engages with one of the holes 300 in the second flat bar 292,for example, to set the plunge or extension depth of the suction pipe122. To readjust the stop mechanism 310 to a different position alongthe second flat bar 292, a user can press the button 314 against thebias of the spring 322 to remove the projection 326 from the hole 300and realign the stop mechanism 310 with a different hole 300. Asmentioned above the first flat bar 288 is attached to the housing 318for movement therewith relative to the second flat bar 292 to set theplunge depth of the suction tube 122.

With reference to FIGS. 8 and 9 , the dust collector 110 includes afilter 346 supported by at least one of the housing 118 and the dustcontainer 134. In the illustrated embodiment of the dust collector 110,the filter 346 includes a housing 348, a pleated element 350 within thehousing 348, and a rim 354 surrounding the pleated element 350. The rim354 is trapped between the dust container 134 and the housing 118 whenthe dust container 134 is attached to the housing 118. Alternatively,the dust collector 110 may incorporate additional structure for securingthe filter 346 to the dust container 134 prior to the dust container 134being attached to the housing 118. When the dust container 134 isremoved from the housing 118, the filter 346 is accessible and removablefrom the dust container 134 for servicing and/or replacement by merelypulling the filter 346 (by, for example, grasping the rim 354) from thedust container 134 after the dust container 134 has been removed ordetached from the housing 118. The filter 346 may be configured as ahigh efficiency particulate air (“HEPA”) filter 346.

The filter 346 is oriented within the dust container 134 in an inclinedor an oblique manner relative to an axis 360 of the dust collector 110.As such, it is expected that at least a portion of the filter 346 willremain exposed when the dust container 134 is nearly filled with dust,regardless of the orientation of the dust collector 110 while in use.Particularly, the pleated element 350 of the filter 346 extends into theinterior of the dust container 134, and at least a portion of thepleated element 350 is expected to remain exposed when the dustcontainer 134 is nearly filled with dust, regardless of the orientationof the dust collector 110 while in use. Optionally, the dust collector110 may include a secondary filter (e.g., a porous plate, a screen,etc.) positioned between the fan 130 and the filter 346 to inhibitparticles that may have bypassed the filter 346 from being impacted bythe fan 130. Furthermore, the secondary filter may help protect the fan130 when the dust container 134 is not connected to the dust collector110. Such a secondary filter may be permanently affixed to the housing118 and non-removable from the housing 118. Such a secondary filter mayalso include a fine pore size, such that any particles bypassing boththe filter 346 and the secondary filter are sufficiently small to notdamage the fan 130.

With reference to FIG. 10 , the dust collector 110 may include a vacuumhose adapter 180 configured to connect to an external vacuum source (notshown). Typically, the dust is sucked through the suction pipe 122 andis collected in a dust container 134. The dust container 134 can then beremoved to empty the dust container 134. However, when excessive amountsof dust are being dispelled into the dust container 134, a user willhave to repeatedly remove the dust container 134, interrupting theirproductivity. Therefore, the vacuum hose adapter 180 may be attached tothe end of the suction pipe 122, so that the dust container 134 can beremoved and a hose from an external vacuum source can be attached to thevacuum hose adapter 180. This allows for a large vacuum source, such asa portable shop vacuum, to be used with the power tool 1 via the dustcollector 110. In the illustrated embodiment, the vacuum hose adapter180 can be threadably coupled to the hose. In other embodiments, othertypes of connections can be used to couple the end of the suction pipe122 to a vacuum hose.

Furthermore, the dust collector 110 may include a filter cleaningmechanism configured to knock dust off of the filter 346. With referenceto FIGS. 8 and 11 , in one embodiment, a filter cleaning mechanism 372is automatically actuated when the fan 130 of the dust collector 110transitions from an active state to an inactive state. A controller (notshown) controls an actuator 374 to strike or impact the filter 346 toshake debris from the filter 346. Triggering of the actuator 374 may bebased on detection of inactivity of the fan 130 or inactivity of themotor 126. As used herein, the fan 130 transitions from the active stateto the inactive state when the fan 130 stops rotating, or when the fan130 slows to a rotational speed below a predetermined threshold suchthat the airflow induced by the fan 130 has effectively stopped. Thecontroller may monitor an indicator of the rotational state of the fan130. In some embodiments, the controller may be configured to monitorthe rotation of the fan 130 by using a Hall-effect sensor for directlydetecting the rotational speed of the fan 130 (e.g., by using a magnetthat rotates with the fan 130). In another embodiment, the fan 130transitions from the active state to the inactive state when the motor126 is no longer transmitting a rotational force to the fan 130.Similarly, the motor 126 can transition from an active state to aninactive state when the motor 126 stops rotating or when the motor 126slows to a predetermined threshold of rotational speed. For example, thecontroller may monitor a sensor that detects the voltage or currentapplied to the motor 126 to determine whether the motor 126 hastransitioned from the active state (i.e., providing torque to the fan130) to the inactive state.

In the illustrated embodiment, the actuator 374 is a solenoid 378 thatcan be actuated to strike the filter 346 and shake dust from the filter346. As shown in FIGS. 12A and 12B, the solenoid 378 includes a coil380, a plunger 382 arranged to slide within the coil 380, and a pin 384on the end of the plunger 382. When the controller detects that the fan130 has transitioned from the active state to the inactive state, thecontroller energizes the coil 380 of the solenoid 378 to move theplunger 382 and the pin 384 from a first position (shown in FIG. 12A) toa second position (shown in FIG. 12B). Specifically, FIG. 12Aillustrates the solenoid 378 in a rest state and FIG. 12B illustratesthe solenoid 378 in an energized state. When the controller fires thesolenoid 378, the pin 384 rotates a bell crank 388 (FIG. 8 ), which, inturn, impacts with the filter 346 and knocks off dust. In someembodiments, the bell crank 388 may not rotate, but instead may transferthe force from the solenoid 378 to the filter 346 without rotating. Inparticular, the bell crank 388 is rotatable about a pivot 392, such thatwhen the pin 384 engages the bell crank 388, the bell crank 388 rotatesand engages with the rim 354 of the filter 346. In some embodiments, thesolenoid 378 may be energized by the controller to impact the filter 346three times over a one second time period.

Notably, in the embodiment illustrated in FIG. 11 , the bell crank 388is arranged to contact the rim 354 of the filter 346 in a directionparallel to the face of the filter 346 (i.e., parallel to the plane ofthe pleated element 350). By impacting the filter 346 in a directionparallel to face of the filter 346, force is concentrated in removingdust from the pleated element 350. Accordingly, less force is wasted asbeing absorbed into the housing 348 of the filter 346, as compared tothe bell crank 388 impacting the filter 346 in a direction perpendicularto the face of the filter 346.

However, in some embodiments, it may be desirable to arrange theactuator 374 to engage the front face of the filter 346. For example,FIG. 13 illustrates a more simplistic filter cleaning mechanism 400. Inthis embodiment, the filter cleaning mechanism 400 has fewer elements,and a solenoid 378 a is arranged to make direct contact with the filter346. In other words, the filter cleaning mechanism 400 does not includea bell crank to impart the force from the solenoid 378 a to the filter346.

FIG. 14 illustrates a filter cleaning mechanism 450 according to yetanother embodiment. In the illustrated embodiment, the actuator 374 isin the form of a clutch bearing 454 (i.e., a one-way bearing) locatedbetween the shaft of the motor 126 and a rotatable plate 462 having aplurality of cogs 466. Under normal operation, the motor 126 and the fan130 rotate about a rotational axis 463 in a first direction (i.e., in acounter clockwise direction in FIG. 14 ). When rotating in the firstdirection, the torque from the motor 126 is not transferred to the plate462. However, once the fan 130 transitions from the active state to theactive state (i.e., slows to a stop or slows to below a predeterminedthreshold speed), the motor 126 is configured to pulse in a second, or areverse direction (i.e., in a clockwise direction in FIG. 14 ). Due tothe effect of the clutch bearing 464, torque is transferred to the plate462 when the motor 126 pulses in the reverse direction. The cogs 466extending from the plate 462 sequentially engage a linkage 468, which inturn, impacts the filter 346. In the illustrated embodiment, the linkage468 rotates about a pivot 472. Similar to the bell crank 388, thelinkage 468 can be arranged to impact the rim 354 of the filter 346 in adirection parallel to the face of the filter 346 (i.e., parallel to theplane formed by the rim 354).

FIGS. 15A-15C illustrate yet another embodiment of a filter cleaningmechanism 500. Specifically, in the sequenced images of FIGS. 15A-15Cillustrate the filter cleaning mechanism 500 in a neutral position (FIG.15A), a ready or a loaded position (FIG. 15B), and an actuated or areleased position (FIG. 15C). The suction pipe 122 includes a pair ofprojections 504, 508 extending from a lower surface of the suction pipe122. When the suction pipe 122 is extended out of the housing 118 of thedust collector 110 from the neutral position (FIG. 15A) to the readyposition (FIG. 15B), the first projection 504 engages with a hammer 512to rotate the hammer 512 in a first direction (i.e., clockwise in FIGS.15A-15C). Specifically, the hammer 512 is rotated against the force of ahammer spring 516. An underside of the hammer 512 includes a lockingslot 518 configured to receive a trigger 520 which holds the hammer 512away from the filter 346 against the urging of the hammer spring 516. Inparticular, the hammer 512 includes a V-shaped locking slot 518 thatengages with a pin 524 extending from the trigger 520. The rotation ofthe hammer 512 against the hammer spring 516 bias places the hammer in a“loaded position.”

During operation of the power tool 1, the suction pipe 122 retracts intothe housing 118 of the dust collector 110 (i.e., towards the right inFIGS. 15A-15C). Once the user finishes drilling, the suction pipe 122returns to its initial position (towards the left in FIGS. 15A-15C). Asthe suction pipe 122 returns, the second projection 508 on the undersideof the suction pipe 122 engages the trigger 520, causing it to pivotabout an axis and remove the pin 524 from the slot 518, thus disengagingthe hammer 512 from the trigger 520 and releasing the hammer 512 so itcan pivot from the loaded position (FIG. 15B) to the actuated position(FIG. 15C). The force of the hammer spring 516 pulls the hammer 512toward the filter 346 and the hammer 512 strikes the filter 346,knocking dust off of the filter 346. A trigger spring 528 then biasesthe trigger 520 back to its original position, as shown in FIG. 15A.

Accordingly, several of the filter cleaning mechanisms provided hereinare automatic filter cleaning mechanisms, which are actuatedautomatically without involvement of the user. In other embodiments, amanually loaded filter cleaning mechanism may be used, wherein a userprovides the loading force on an actuator configured to knock dust offof the filter 346. Similarly, in other embodiments, the actuator may bemechanically loaded. For example, the actuator of the filter cleaningmechanism may be mechanically loaded by air diverted by a separatemechanical mechanism. In yet another embodiment, the actuator of thefilter cleaning mechanism may be actuated upon timing intervals measuredduring the duration of time that the power tool is in operation.

Furthermore, in some embodiments, the dust collector 110 includes amonitoring system that monitors the air flow through the dust collector110 to detect obstructions or clogs in the filter 346. For example, asshown in FIG. 8 , the dust collector 110 may include one or more sensors405A, 405B that measure a characteristic value of the airflow toidentify changes in the air flow velocity upstream and/or downstream ofthe filter 346. For example, in one embodiment of the monitoring system,the sensor 405B detects the pressure of the space between the filter 346and the fan 130. A pressure value below a predetermined threshold wouldindicate a higher than expected vacuum drawn by the fan 130, thusindicating that an obstruction exists (i.e., that the filter 346 isclogged beyond an acceptable limit). In another embodiment of themonitoring system, the output of the sensors 405A, 405B may be used tocalculate a pressure differential on the opposite sides of the filter346. Then, a pressure differential value above a predetermined thresholdwould indicate a higher than expected vacuum drawn by the fan 130, thusindicating that the filter 346 is clogged beyond an acceptable limit. Inother embodiments, the sensors 405A, 405B may measure the speed of theairflow upstream and/or downstream of the filter 346. In this embodimentthe sensors 405A, 405B may be, for example, Venturi meters. In anembodiment only using the sensor 405B, a detected airflow speed below apredetermined threshold would indicate a higher than expected vacuumdrawn by the fan 130, thus indicating that the filter 346 is cloggedbeyond an acceptable limit. And, in an embodiment using both sensors405A, 405B, the output of the sensors 405A, 405B may be used tocalculate a differential in the air speed on the opposite sides of thefilter 346. Then, an air speed differential value above a predeterminedthreshold would indicate a higher than expected vacuum drawn by the fan130, thus indicating that the filter 346 is clogged beyond an acceptablelimit.

If the pressure or the air flow velocity drop below a predeterminedthreshold, or the pressure or air speed differential exceed apredetermined threshold, the controller may inform a user that air flowthrough the filter 346 has been reduced. For example, the controller mayinitiate an audible notification, such as a beep or other noiseindicating there may be an obstruction. The controller may provide avisible notification, such as a flashing light, or any other type ofnotification, such as tactile or otherwise, indicating there may be anobstruction in or around the filter 346. In some embodiments, themonitoring system utilizes multiple predetermined threshold values toindicate the severity of the obstruction. For example, in oneembodiment, when the characteristic value detected by the sensors 405A,405B (i.e., pressure or air speed) drops below a first predeterminedthreshold, the controller may initiate a single audible noise, or mayprovide a certain color light (e.g., blue) to inform the user that theremay be a small obstruction on the filter 346. Then, when thecharacteristic value detected by the sensors 405A, 405B drops below asecond predetermined threshold, the controller may initiate multipleaudible noises, or may provide a different color light (e.g., red) toinform the user that there may be a larger obstruction.

With continued reference to FIG. 8 , in some embodiments, the monitoringsystem may include a sensor 410 to monitor changes in the current drawnby the electric motor 126 driving the fan 130. As the filter 346 becomesblocked, the fan 130 will not be able to move as much air across thefilter 346 and will be doing less work. This results in a reducedcurrent being drawn by the electric motor 126. In other words, when thefilter 346 is blocked, there is no air for the fan 130 to move and anear-vacuum state is formed in proximity of the fan 130. Accordingly,the fan 130 is spinning within a space with little air resistance, thuscausing the fan 130 to draw a current that is lower than the normalload. Therefore, a lower current drawn by the electric motor 126indicates the existence of an obstruction. The sensor 410 monitors thecurrent drawn by the electric motor 126 to identify a drop in currentbelow a predetermined threshold corresponding to a clogged or partiallyclogged filter 346. In some embodiments, the monitoring system may useinput from all, or different combinations, of the sensors 405A, 405B,410 to detect that the filter 346 is clogged beyond an acceptable limit.

Similar to the monitoring system described above using input from thesensors 405A, 405B, the monitoring system that uses input from thesensor 410 may also provide staged notifications to the user when thesensor 410 identifies a possible obstruction or clog in the filter 346.When the current drops below a predetermined threshold, the controllermay indicate via audible or visual cue that there has been a change incurrent and that the filter 346 may be clogged.

As will be understood by a person of ordinary skill in the art, themonitoring system may also be used with power tools having on boardvacuum systems. For example, the dust collection system may be housedwithin the power tool housing. Accordingly, the power tool may have a onboard dust collection system that includes the monitoring systemdescribed above. Likewise, the filter cleaning mechanisms describedherein may also be used with power tools having on board vacuum systems.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A dust collector for use with a hand-held powertool, the dust collector comprising: a housing; a motor positioned inthe housing; a telescoping suction pipe coupled to the housing; asuction fan coupled to the motor and operable to generate a vacuum inthe suction pipe; a dust container coupled to the housing and positionedupstream of the suction fan; a filter at least partially arranged in thedust container; and a filter cleaning mechanism including a solenoidconfigured to be actuated by a controller to dislodge dust from thefilter when either the motor or the suction fan transitions from anactive state to an inactive state.
 2. The dust collector of claim 1,wherein the suction fan transitions from the active state to theinactive state when one of: the suction fan stops rotating; or arotational speed of the suction fan slows to less than a predeterminedthreshold rotational speed.
 3. The dust collector of claim 1, whereinthe motor transitions from an active state to an inactive state when oneof: the motor stops rotating; or a rotational speed of the motor slowsto less than a predetermined threshold rotational speed.
 4. The dustcollector of claim 1, wherein the motor transitions from an active stateto an inactive state when the motor stops providing torque to thesuction fan.
 5. The dust collector of claim 1, wherein in response tobeing actuated, the solenoid impacts the filter to dislodge dust fromthe filter.
 6. The dust collector of claim 1, wherein the solenoidincludes a pin movable between a first position and a second position inresponse to the solenoid being actuated.
 7. The dust collector of claim6, wherein the filter cleaning mechanism further comprises a bell crank,and wherein when the pin moves from the first position to the secondposition, the pin drives the bell crank to impact the filter, therebydislodging dust therefrom.
 8. The dust collector of claim 7, wherein thebell crank is configured to impact a rim of the filter along a directionparallel to a face of the filter.
 9. A dust collector for use with ahand-held power tool, the dust collector comprising: a housing; a motorhaving a motor shaft rotatable in a first rotational direction and in asecond rotational direction opposite the first rotational direction; atelescoping suction pipe coupled to the housing; a suction fan coupledto the motor and operable to generate a vacuum in the suction pipe whenthe motor shaft rotates in the first rotational direction; a dustcontainer coupled to the housing and positioned upstream of the suctionfan; a filter at least partially arranged in the dust container; and afilter cleaning mechanism configured to dislodge dust from the filterwhen the motor shaft rotates in the second rotational direction.
 10. Thedust collector of claim 9, wherein the filter cleaning mechanismcomprises a clutch bearing coupled between the motor shaft and arotatable plate.
 11. The dust collector of claim 10, wherein the clutchbearing does not transfer torque from the motor shaft to the plate whenthe motor shaft rotates in the first rotational direction, and whereinthe clutch bearing transfers torque from the motor to the plate when themotor shaft rotates in the second rotational direction.
 12. The dustcollector of claim 10, wherein the filter cleaning mechanism furthercomprises a linkage that impacts the filter in response to being engagedby the plate.
 13. The dust collector of claim 12, wherein the plateincludes a plurality of cogs, and wherein when the plate rotates, thecogs sequentially engage the linkage to cause the linkage to impact thefilter.
 14. A dust collector for use with a hand-held power tool, thedust collector comprising: a housing; a motor positioned in the housing;a telescoping suction pipe coupled to the housing and configured totelescope toward and away from the housing; a suction fan coupled to themotor and operable to generate a vacuum in the suction pipe; a dustcontainer coupled to the housing and positioned upstream of the suctionfan; a filter at least partially arranged in the dust container; and afilter cleaning mechanism including a hammer movable between a loadedposition, in which the hammer is biased toward engagement with thefilter, and a released position, in which the hammer impacts the filterto dislodge dust therefrom; wherein as the suction pipe telescopestoward and away from the housing, the suction pipe engages the filtercleaning mechanism to cause the hammer to move between the loaded andreleased positions.
 15. The dust collector of claim 14, wherein thefilter cleaning mechanism further comprises a hammer spring that biasesthe hammer toward the released position when the hammer is in the loadedposition.
 16. The dust collector of claim 14, wherein the filtercleaning mechanism further comprises a trigger configured to hold thehammer in the loaded position.
 17. The dust collector of claim 16,wherein the suction pipe includes a first projection, and wherein whenthe suction pipe telescopes toward the housing, the first projectionengages the hammer to move the hammer from the released position to theloaded position.
 18. The dust collector of claim 17, wherein the suctionpipe further includes a second projection, and wherein when the suctionpipe telescopes away from the housing, the second projection engages thetrigger to release the hammer from the loaded position.
 19. The dustcollector of claim 16, wherein the filter cleaning mechanism furthercomprises a trigger spring that biases the trigger into engagement withthe hammer.
 20. A dust collector for use with a hand-held power tool,the dust collector comprising: a housing; a motor positioned in thehousing; a suction pipe coupled to the housing; a suction fan coupled tothe motor and operable to generate a vacuum in the suction pipe; a dustcontainer coupled to the housing and positioned upstream of the suctionfan; a filter at least partially arranged in the dust container; and amonitoring system configured to detect clogs in the filter by detectinga characteristic value of the dust collector and determining whether thecharacteristic value exceeds a predetermined threshold.
 21. The dustcollector of claim 20, wherein the monitoring system is furtherconfigured to issue a notification indicative of a clog in the filter.22. The dust collector of claim 21, wherein the notification includesone of an audible notification or a visible notification.
 23. The dustcollector of claim 20, wherein the monitoring system includes a firstpressure sensor that detects a first pressure within a space between thefilter and the suction fan, and wherein the characteristic value is thefirst pressure.
 24. The dust collector of claim 20, wherein themonitoring system includes a first pressure sensor that detects a firstpressure within a space between the filter and the suction fan, and asecond pressure sensor that detects a second pressure within the dustcontainer, and wherein the characteristic value is a pressuredifferential between the first pressure and the second pressure.
 25. Thedust collector of claim 20, wherein the monitoring system includes afirst Venturi meter that detects a first airflow speed within a spacebetween the filter and the suction fan, and wherein the characteristicvalue is the first airflow speed.
 26. The dust collector of claim 20,wherein the monitoring system includes a first Venturi meter thatdetects a first airflow speed within a space between the filter and thesuction fan, and a second Venturi meter that detects a second airflowspeed within the dust container, and wherein the characteristic value isa differential between the first airflow speed and the second airflowspeed.
 27. The dust collector of claim 20, wherein the monitoring systemdetects a current drawn by the motor, and wherein the characteristicvalue is the detected current.